Department of Biological Geological and Environmental Sciences, University of Bologna, 40126, Bologna, Italy.
La Venta Geographic Explorations Association, 31100, Treviso, Italy.
Sci Rep. 2018 Dec 4;8(1):17569. doi: 10.1038/s41598-018-35532-y.
Chemical mobility of crystalline and amorphous SiO plays a fundamental role in several geochemical and biological processes, with silicate minerals being the most abundant components of the Earth's crust. Although the oldest evidences of life on Earth are fossilized in microcrystalline silica deposits, little is known about the functional role that bacteria can exert on silica mobility at non-thermal and neutral pH conditions. Here, a microbial influence on silica mobilization event occurring in the Earth's largest orthoquartzite cave is described. Transition from the pristine orthoquartzite to amorphous silica opaline precipitates in the form of stromatolite-like structures is documented through mineralogical, microscopic and geochemical analyses showing an increase of metals and other bioessential elements accompanied by permineralized bacterial cells and ultrastructures. Illumina sequencing of the 16S rRNA gene describes the bacterial diversity characterizing the consecutive amorphization steps to provide clues on the biogeochemical factors playing a role in the silica solubilization and precipitation processes. These results show that both quartz weathering and silica mobility are affected by chemotrophic bacterial communities, providing insights for the understanding of the silica cycle in the subsurface.
结晶态和非晶态二氧化硅的化学活动性在许多地球化学和生物过程中起着根本作用，而硅酸盐矿物是地壳中最丰富的成分。尽管地球上最早的生命证据是在微晶硅质沉积物中被化石化的，但对于在非热和中性 pH 条件下细菌对二氧化硅活动性的功能作用，人们知之甚少。在这里，描述了在地球上最大的正交石英洞中发生的一种微生物对二氧化硅迁移事件的影响。通过矿物学、微观和地球化学分析，记录了从原始正交石英到非晶态蛋白石沉淀物的转变，以层状结构的形式出现类似于叠层石。结果表明，金属和其他生物必需元素的增加伴随着矿化细菌细胞和超微结构，伴随着金属和其他生物必需元素的增加。16S rRNA 基因的 Illumina 测序描述了表征连续非晶化步骤的细菌多样性，为在硅溶解和沉淀过程中起作用的生物地球化学因素提供了线索。这些结果表明，石英风化和二氧化硅迁移都受到化能细菌群落的影响，为理解地下的二氧化硅循环提供了依据。
